Sulphur metabolism in colon cancer tissues: a case report and literature review

Sulphur-containing compounds have been linked to colorectal cancer by factors such as the presence of methyl mercaptan in intestinal gas and long-term dietary intake associated with sulphur-metabolizing microbiota. Therefore, this current case report hypothesized that active sulphur metabolism in colorectal cancer results in the formation of sulphur compounds in the intestine and, thus, examined sulphur metabolites possibly associated with sulphur respiration in colon cancer tissues. The patient was a 73-year-old female that underwent laparoscopic right hemicolectomy for ascending colon cancer. During the surgery, colon cancer tissues and normal intestinal mucosa samples were collected. After optimizing the sample concentrations for homogenization (pre-treatment), the samples were stabilized using a hydroxyphenyl-containing derivative and the relevant metabolites were quantified using liquid chromatography with tandem mass spectrometry. The results showed that cysteine persulfide and cysteine trisulfide levels were higher in colon cancer tissues than in normal mucosal tissues. Thus, sulphur metabolism, possibly sulphur respiration, is enhanced in colon cancer tissues.

DiSCo: a sequence-based type-specific predictor of Dsr-dependent dissimilatory sulphur metabolism in microbial data

Current methods in comparative genomic analyses for metabolic potential prediction of proteins involved in, or associated with the Dsr (dissimilatory sulphite reductase)-dependent dissimilatory sulphur metabolism are both time-intensive and computationally challenging, especially when considering metagenomic data. We developed DiSCo, a Dsr-dependent dissimilatory sulphur metabolism classification tool, which automatically identifies and classifies the protein type from sequence data. It takes user-supplied protein sequences and lists the identified proteins and their classification in terms of protein family and predicted type. It can also extract the sequence data from user-input to serve as basis for additional downstream analyses. DiSCo provides the metabolic functional prediction of proteins involved in Dsr-dependent dissimilatory sulphur metabolism with high levels of accuracy in a fast manner. We ran DiSCo against a dataset composed of over 190 thousand (meta)genomic records and efficiently mapped Dsr-dependent dissimilatory sulphur proteins in 1798 lineages across both prokaryotic domains. This allowed the identification of new micro-organisms belonging to Thaumarchaeota and Spirochaetes lineages with the metabolic potential to use the Dsr-pathway for energy conservation. DiSCo is implemented in Perl 5 and freely available under the GNU GPLv3 at https://github.com/Genome-Evolution-and-Ecology-Group-GEEG/DiSCo.

The Effect of Introgression of an R2R3 MYB Transcription Factor on Sulphur Metabolism in Brassica oleracea

BackgroundA diet rich in cruciferous vegetables is reported to have beneficial health effects, partially mediated by 4-methylsulfinylbutyl glucosinolate, or glucoraphanin, which is predominantly found within broccoli (Brassica oleracea var italica). We describe the downstream effects on transcription and metabolism in broccoli following the introgression of a genetic variant of MYB28 into broccoli from a wild Brassica relative which has previously been associated with enhancement of glucoraphanin.ResultsWhole genome sequencing, RNA expression and metabolite analyses were used to characterise the consequences of the introgression of either one or two copies of a genetic variant of the MYB28 transcription factor into a commercial broccoli genetic background. The introgression of the variant of MYB28 resulted in enhanced expression of genes involved in primary sulphate assimilation, sulphur metabolism and aliphatic glucosinolate biosynthesis, and enhanced accumulation of 4-methylsulphinyl butyl glucosinolate in florets. Other changes in transcription that may be related to non-targeted introgression events are reported. There were no consistent effects upon sulphur metabolites pools, apart from methionine-derived glucosinolates.ConclusionThis study illustrates the downstream effects on transcription and metabolism of the introgression of a genetic variant of MYB28 from a wild species into a commercial broccoli genotype.

Plant sulphur metabolism is stimulated by photorespiration

Intense efforts have been devoted to describe the biochemical pathway of plant sulphur (S) assimilation from sulphate. However, essential information on metabolic regulation of S assimilation is still lacking, such as possible interactions between S assimilation, photosynthesis and photorespiration. In particular, does S assimilation scale with photosynthesis thus ensuring sufficient S provision for amino acids synthesis? This lack of knowledge is problematic because optimization of photosynthesis is a common target of crop breeding and furthermore, photosynthesis is stimulated by the inexorable increase in atmospheric CO2. Here, we used high-resolution 33S and 13C tracing technology with NMR and LC-MS to access direct measurement of metabolic fluxes in S assimilation, when photosynthesis and photorespiration are varied via the gaseous composition of the atmosphere (CO2, O2). We show that S assimilation is stimulated by photorespiratory metabolism and therefore, large photosynthetic fluxes appear to be detrimental to plant cell sulphur nutrition.